Silicon photonics is an expanding field due to its promise for reducing the cost and increasing performance of optical data communication systems. Functionalities such as detection and modulation can be implemented with devices defined in silicon, since carrier collection and generation are involved. However, integration of optical components and waveguides and the fabrication thereof with existing silicon processes such as CMOS, bipolar, and BiCMOS-style processes remain a challenge due to the fundamentally different material systems, operating principles, and state-of-the-art feature sizes/dimensions.
For example, one difficulty with such processes is that dielectric waveguides are typically large, e.g., in the range of micrometers, and can span dimensions from submicron (typically in tapered structures) up to tens of microns in order to match profiles with large-core fibers. The height of dielectric waveguides is thus much larger than the typical back-end layer thickness in a state-of-the-art integrated circuit and can be difficult to integrate both structurally and in manufacturing processes.